The Bell P-39 Airacobra was a peculiar mid-engine WWII fighter aircraft. While it had relatively poor performance at altitudes due to the un-supercharged Allison engine, the Airacobra saw acceptable service in the Pacific theatre as well as the Eastern front when flown by soviet pilots through the lend-lease program. The pilot sat in front of the engine, which drove a shaft under the pilot's feet to the propeller. The reason for this was mainly to fit an Oldsmobile T9 37mm cannon in the nose, similar to the cannons fitted to light tanks of the time. The -Q5 variant of the Airacobra (which is what I have modelled) also sported 4x12.7mm (.50 caliber) M2 machine guns, 2 in wing pods and 2 in the nose above the 37mm cannon.
It wasn't the best performing aircraft around, but the 37mm cannon gave it an edge against ground targets and any aircraft unlucky enough to stray in front of it. The P-39 also used a tricycle landing gear system, which was relatively unheard of at the time.
Please read up on this interesting technological marvel: https://en.wikipedia.org/wiki/Bell_P-39_Airacobra
I realize I haven't modelled it perfectly, but I love this aircraft and I've captured it very closely. If you'd like to edit the file and remix it, I've included the sketchup source file.
I also haven't printed it yet. It might work better to make it in parts. I'll cut it up and re-upload it if that's the case.
Edit: I finally got around to cutting it up and laid the parts out in 4 groups for printing. You'll want supports for the wing gunpods and tail section, but it should be pretty straight forward.
Be careful around the guns and wingtips when removing support
Sketchup via a 3 view drawing.